Need some science help.

[timbudtwo]

Okay, So I have some very pure Chromium(III) Oxide that I would like to test out as a colorant for a soap. However, it is not in a finely powdered form. I have looked at the msds of every chromium green mica/oxide and it has Chromium(III) oxide/hydroxide listed as the main or sole constituent.

Looking at the msds of Chromium oxide, it is slightly soluble in an alkaline solution. However, I have had zero success with dissolving this stuff in anything. Ive tried just water, alcohol, and hot lye water. Everything I have read about this stuff says this should be working. Has anyone experimented with Chromium colors (Chromium green ultramarine is the same thing btw)?

I know what I have is Chromium (III) Oxide because it was prepared from the decomposition of Ammonium Dichromate.

All help is appreciated!

 

[rubyslippers]

I often use Chronium green oxide as a colorant however mine is already in a liquid form but it has an oily appearance to it. Don't know if this will work but can't hurt to try....a little gylcerin maybe?

 

[timbudtwo]

The problem isn't just dissolving it. Because its not a fine powder, it wouldn't look good even if I put it in something that had a higher viscosity to hold the particles in suspension.
Thanks though!

 

[donniej]

If I were trying to get it into a powder form I'd start by dissolving it in acid. When you nuetralize the acid, it should fall out of solution as a powder... unless the acid and following nuetralization convert it into something else. Either way, after it's precipitated out of solution you'll need to wash is to remove the salt which is created when you nuetralized the acid.

Muriatic acid from the hardware store is (33%) HCL or hydrochloric acid. When nuetralized with lye, NaOH it will form NaCL or table salt. You can rinse the salt out of your CrO3 with water using a coffee filter to prevent washing away the CrO3.

 

[Deb]

I get mine in powder form and use either glycerine, or straight oil. So far so good!

 

[timbudtwo]

If I were trying to get it into a powder form I'd start by dissolving it in acid. When you nuetralize the acid, it should fall out of solution as a powder... unless the acid and following nuetralization convert it into something else. Either way, after it's precipitated out of solution you'll need to wash is to remove the salt which is created when you nuetralized the acid.

Muriatic acid from the hardware store is (33%) HCL or hydrochloric acid. When nuetralized with lye, NaOH it will form NaCL or table salt. You can rinse the salt out of your CrO3 with water using a coffee filter to prevent washing away the CrO3.

Well, I do have some H2SO4, and from what I understand will not create chromium chloride (not as innocuous as Cr2O3) as would be created from HCL. I was thinking that I may have needed to hydrate it (with an acid) before I was able to get it to dissolve in the lye mixture. The only other instructions that I was able to find other than wikipedia and merck information was an excerpt from Hydrometallurgy in extraction processes, Volume 1 Here is the excerpt http://books.google.com/books?id=F7...g#v=onepage&q=dissolve chromium oxide&f=false

Problem is it needs to be at about 150psi and at over 400 degrees F.

 

[NancyRogers]

have you tried to grind it and then mix it with some oil? If you have a coffee grinder that you are willing to sacrifice to soap making, that will work. Or you can get a mortor and pestle. That works too. Good luck.

 

[timbudtwo]

have you tried to grind it and then mix it with some oil? If you have a coffee grinder that you are willing to sacrifice to soap making, that will work. Or you can get a mortor and pestle. That works too. Good luck.

I thought the greater viscosity would keep it suspended in soap, but I do not think that the coffee grinder will work on this to powder it up (I haven't tried it yet though.) The stuff is very light and fluffy. The mortal and pestle would work but the only one I have is made of wood and is a souvenir, so I don't want to use that.

 

[mariflo]

I use Chromium (III) Oxide and I mix it with glycerol and add it at trace.
I found that a convenient way to work with it is by mixing it with glycerol and crushing the larger "grains" against the mixing bowl with the back of the spoon till it works into a homogenous paste. It works for me.

 

[zajanatural]

I think I would just pass it up and stick with using the Chromiums that have tested stable for soap making. I suspect that the colors we use are maybe mixed with an additive that allows them to blend easily in any liquid.

 

[timbudtwo]

I think I would just pass it up and stick with using the Chromiums that have tested stable for soap making. I suspect that the colors we use are maybe mixed with an additive that allows them to blend easily in any liquid.

Some of them are, however, it must be listed in their msds. Many are pure.

However, I did solve the problem. I simply mixed it with olive oil (glycerin would have worked too) and it stays suspended just fine. Should have tried the easier solutions first! Ill try the acid/base experiment later.

Thanks

 

[carebear]

actually an MSDS isn't required to have a complete ingredient list.